ALMOST every newer car made today has the pre-cats and if they did notice the headers then there might be a good chance they are gonna fail ya....
I've seen it happen a few times to my friends and the garage said to come back with the stock stuff on or they can't pass the vehicle...

Nissans never dyno close to crank rating. They almost always dyno ~20% lower than the "paper HP measurement". There were even some owners complaining about incorrectly claimed HP #'s that Nissan was making concerning the VQ35(240,245,255,260,280,287 HP versions). 240HP Altimas have been known to make the same power as 255hp Maximas.
Hyundai/Kia/Mazda... already lost $$$ making false HP claims. Nissan is next.

Strom,

The new headers mate right up to the flange at the top of the main cats. Basically the stock config is manifold, pre-cat, main cat, y-pipe...
Now it's header, main cat, y-pipe.

Brent

I know a lot of East coast 2000 Xterras had them as well.

Yup, mine included

Not only that the Sentra's are also guilty of the 20% lower HP raiting over the crank...It's all drive train loss...

Anyone think that the precats and cats could be moved back a little? Cut them out and reweld them so that the headers bolt right up to the precats - then neither is removed.

The only problem I've ever had with headers is that they have higher emmmisions until the engine has warmed up. They *should* pass overall emmisions, but might not pass visual or at start-up (for California?). CARB certification is a pain to get so maybe SLR decided to pass on that or maybe work on getting it and in the meantime release product...who knows. It looks like a great product with quality craftsmanship. I would be interested in knowing where the power comes in; a dyno sheet would be good. When are these going to be available?

I hope they are available unfinished as I have this thing for Swain coatings

Sweet! I've been waiting along time to see this product hit. Ought to make the Gibson exhaust louder being that it's silence is the only thing I dislike about it. Way to go SLR, my tax return is enroute

Well, bad new folks. I was wrong. The first set of cats are the main cats, not the pre-cats. That complicates things a bit, but the loss of the post-cats wouldn't set off the computer, that's good. However, simply pushing the main cats down to where the post-cats were doesn't appear to be particularly simple, there's the matter of the 40-degree kink that is built into the post-cats to turn the exhaust horizontal that you would have to deal with, requiring some custom piping and flanges. You're probably better off going ahead and investing in some generic aftermarket hi-flow cats than trying to relocate the original ones at that point.

Brent

You're right Brent. I was thinking all along that there was more pipe before the cats on the factory manifolds. I just went out and looked and realized what you've been saying. So, these headers do move or eliminate the cats. There would be some custom work going on to install these. One of these days I might give SLR a call and talk to them about moving the cats and everything.

So who is gonna be the first ones to try these headers? Im curios how hard things are gonna be to get them on. I think these are gonna be a pain in the as* I really want these headers. Unfortunatly i can't afford them anytime soon. Its about time a company makes a good performance product for the Xterra.

The install looks like it's gonna be pretty simple to install..Nice and straight forward...

So nobody knows if it's a DIY job?

It doesn't require any special tools, if that's what you mean. About the hardest part is the rusted bolts that live in most exhaust systems.

Do they come with gaskets? They make no mention of it on there site.

Relocation of the cats and the required changes to the exhaust changes will be a bit of a PITA though. Probably need to have a good exhaust shop do the work.

I'm wondering if anyone has seen a dyno sheet on these. My point being where are the gains to be made. If these are racing units I doubt any of us would want them. But then SLR went to the trouble of designing o2 sensor ports and I believe there site states it will bolt right up to your cats. That sounds like street use to me. If they can produce a torque curve that broadens both the top and bottom of the existing curve I'll buy them ASAP. 14 HP is less of a gain than I would expect but lets hope they are equal lenghth runners with smallish tubes and that will give our stock cams, intakes and low compression pistons a good shot at better scavenging. I'm no expert on exhaust but I have built and hot rodded all sorts of vehicles and properly timed scavenging is key to making usable power.
I'm wondering if dual exhaust with maybe a balance tube would be of value. Here in Nevada we do not have a smog check (Washoe and Clark county excluded from the fun) so I might be the ginni pig. Let the good times roll!

SLR's site is mistaken, the "pre cats" are the main ones. Many 2000 models didn't even have the second pair.

Brent

yeah, the lower cats are there to clean up whatever is left over from the cats upstream. BTW, you should replace "many" with "most" in regards to 2000 models.

However, I wonder if the second set of cats will function as main cats? If that's the case then for us 2000 owners it would be a matter of getting two of the cats that go downstream and adding them in. Kinda spendy but maybe doable? If I come up with the money and am ready to buy I'll contact SLR directly and ask how this would work.

Or maybe we one could add some CarSound cats in their place.

That would be easier and cheaper I'm sure.

Brent

Pre Cats, Post Cats, what the hell are you guys talking about? My 2002 Xterra 3.3L only has one set of cats on it. There are two right below the manifolds, one on each side then the "Y" pipe then the muffler. That's all I have.

Am I to understand that these headers will eliminate these two cats? If so, these are a BAD idea.

The first two cats they are talking about is a cocoon looking thing towards the front of the Exhaust....Which I don't believe they are actually cats but I think they are in fact Flex couplers..But I could be wrong....

Someone needs to take some pictures to clear this all up.